Process for the manufacture of continuous refractory fibers



Apnl 3, 1962 H. s. SCHWARTZ 3,028,214

PROCESS FOR THE MANUFACTURE OF CONTINUOUS REFRACTORY FIBERS Filed March3, 1961 2 Sheets-Sheet 1 INVENTOR. HERBERT S. CHWARTZ.

ATTORN EYS H. s. SCHWARTZ 3,028,214 PROCESS FOR THE MANUFACTURE OFCONTINUOUS REFRACTORY FIBERS Filed March 6, 1961 2 Sheets-Sheet 2 April3, 1962 INVENTOR. HERBERT s. SCHWARTZ ATTORNEYS United States Patent3,028,214 PROCESS FOR THE MANUFACTURE OF CONTINUOUS REFRACTORY FIBERSHerbert S. Schwartz, 800 Eppington Drive, Trotwood, Ohio Filed Mar. 3,1961, Ser. No. 93,277 6 Claims. (CI. 18-54) (Granted under Title 35, US.Code (1952), see. 266) The invention described herein maybe'manufactured and used by or for the United States Government forgovernmental purposes without the payment to me of any royalty thereon.

This invention relates to a new and improved process for makingrefractory fibers.

Past practices in making refractory fibers of silica, aluminosilicateand the like have been by heating the end of a rod of the refractorymaterial and drawing a filament away from the rod; by blowing moltenmaterial into filaments; and for refractories with lower melting pointsby melting the refractory material in a multiple orifice crucible anddrawing fibers from the crucible orifices; and the like. For materialswith high melting points, such as silica and aluminosilicate, there areno completely satisfactory materials for crucibles.

Filaments made by the first two of the above mentioned processes havethe limitations of being of non-uniform diameter, of random lengths, ofvarying flexibilities, and of non-uniform tensile strength when used infabrics for high strength, high temperature resistant structurallaminates and the like. Filaments with these limitations are poorlyapplied when used with automatic machinery and result in low gradearticles when used in fabrics of protective types such as in firefighting costumes and the like, whether they ar woven, matted, felted,made into thread, cables or otherwise converted into equipment.

Silica softens at temperatures above 1470 C. which corresponds to 2678F. Aluminosilicate softens at about 1372" C. or 2500 F. Alumina melts atabout 2050" C. or 3722 F. Tantalum melts at about 3000" C. or 5432 F.Tungsten melts at 3370 C. or 6098" F. An acetylene-oxygen flame has aflame temperature of about 2632" C. or 4770 F.

The subject matter of this invention and its general object is theprovision of an improved process for making refractory fibers orfilaments. The fibers that are produced by the method described hereinstructurally are more nearly of uniform diameter than those previouslyproduced and are of uniform tensile strength and quality.

The invention also has for an object the provision of a compact andsimply operated and controlled battery of filament producing units.

Apparatus that is used in practicing the present invention isillustrated in the accompanying drawing wherein:

FIG. 1 is a perspective view of an apparatus that is used in followingthe process that is disclosed herein;

FIG. 2 is a view taken from the line 2-2 in FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line 3 3 of FIG.2; and

FIGS. 4, 5 and 6 are plan views of doctor blades that work the moltenrefractory material preparatory to its being drawn as a filament orthread.

In FIG. 1 of the accompanying drawing is illustrated a battery of discsof refractory material from which a plurality of filaments are drawn inthe practice of the present invention.

The process that is contemplated hereby is the drawing of a filamentfrom a slowly rotated and peripherally heated refractory disc 1 made ofsilica, aluminosilicate, mixtures thereof or the like, and using adoctor blade for hot working the refractory in its molten state.

The disc 1 illustratively is mounted on a core 2 and has "icea flame 3applied substantially tangentially to its periphery in the direction ofthe rotary motion of the disc. The flame 3 liquefies the refractorymaterial of silica, aluminosilicate or the like, which it contacts. Adoctor blade 4 is applied to the periphery of the disc 1 and adjacentthe tip of the flame 3, such that it acts as a baflle around which theslowly moving fluid refractory must flow. The doctor blade imparts apuddling or a mixing action into the molten silica, aluminum silicate orthe like refractory material of which the peripheral edge of the disc 1is made as the disc 1 is rotated through a gear train by a motor 10. Thedoctor blade 4 works and mixes the molten refractory to remove seeds,air bubbles, undesirable variations in viscosities from abrupttemperature gradients and the like for the purpose of impartinguniformity in composition, texture and structure to a filament 5 that isdrawn from the periphery of the disc 1 just after it passes the doctorblade 4.

In drawing a filament of glass from a pool of molten glass, it is commonpractice to touch the surface of the molten glass with the tip of asolid glass rod and draw the glass rod away from the pool of moltenglass, carrying the end of the glass filament to a desired destination.This technique is used in initiating the withdrawal of a filament fromthe pool of molten refractory material on the edge of or on theperiphery of the disc 1 after the molten refractory material has beenpuddled by the doctor blade while the disc 1 is rotating or after thedoctor blade has worked or has mixed the liquid refractory material thatcontinues to be carried along by the circumferential travel of the disc1 as it is rotated by the motor 10.

The doctor blade 4 illustratively is made of tungsten or tantalum at thetip, welded to a support of steel, brass or the like that is positivelymounted to maintain a firm and predetermined position with respect tothe flame 3.

The tungsten or tantalum tipped doctor blade terminates at its distal orunattached end in a preferred contour, of which those shown in FIGS. 4,5 and 6 are illustrative.

The doctor blade tip 4' in FIG. 4 is laterally flat from a projectionmidway between its edges and engages the molten refractory materialunder the flame 3 at the periphery of the disc 1 in a laterallyspreading flow starting midway between the lateral edges of the disc.

The docotor blade tip 4" is wedged or tapered to converge toward its tipand engages the molten refractory material under the flame 3 an optimumspreading amount intermediate the lateral edges of the disc.

The doctor blade tip 4" is tapered from its lateral edges and is slottedat its tip to preform the filament midway between the lateral edges ofthe disc 1.

All of the doctor blade mountings preferably are adjustable, such as bythe hinge 9 in FIG. 2 or the like, so that at the beginning ofoperations the refractory material may be brought to its melting pointbefore the tip of the doctor blade is depressed into the material and sothat at the end of operations the doctor blade may be lifted up out ofthe molten refractory material before it returns to its solid state.

The discs 1 are rotated at a sufiiciently slow and uniform rate beneaththe flames 3 to impart continuously a substantially uniform diameter tothe filaments 5. The flames 3 illustratively are of acetylene emittedfrom bumer nozzles 6 that are fed from a gas supply pipe 7. The nozzles6 preferably are adjustable with respect to the gas pipe 7.

The core 2 has a plurality of refractory discs I mounted thereon in adesired manner, such as by the drum being grooved axially along itsperiphery at both ends of a common diameter, with each of the axialgrooves opening into short circumferential grooves to provide bayonetslot mounts for the discs.

Each disc 1 has projecting from its radially inner edge a pair ofdiametrically opposed keys 8 and 8' that are caused to enter the axialgrooves and lodge in the bayonet slots in mounting the discs on the core2 or in disassembling the structure when the refractory has been usedup.

The process is followed simultaneously for each disc I mounted on thedrum 2 to provide a steady flow of a bank of filaments 5. The bank offilaments 5 may be woven directly into fire resistant fabrics, cords,cables and the like, or may be passed continuously through a mixture oflubricating oil and starch or the like and stored on spools or bobbinsfor future use.

The disc 1 is made of a refractory such as silica, aluminosilicate,mixtures of silica with alumina, or the like. A representative mixtureof refractory out of which the discs 1 are made consists of by weight,55 percent silica, 41 percent alumina and 4 percent zirconia. Therefractory is mixed and ground to a uniform and homogeneous compositionand then is cast to a desired shape.

In making a representative disc 1 under laboratory conditions oftemperature and pressure pure silica is ground to about 100 mesh and ismixed with a water dispersion of celloidal silica gel as binder to makea slurry. The slurry is poured into the disclike cavity of a mold madeof a plastic, silicon rubber, graphite, a ceramic, metal or the like.The silica slip molded disc is dried at 230 F. for from 30 minutes toone hour and then is removed from the mold and is fired in an oven at1800" F. for one-half hour. The resulting fired disc is then ready foruse and is of a preferred contour, mounting and operation.

The illustrative installation shown in the accompanying drawingcomprises a plurality of the refractory discs I mounted on the core 2.The discs 1 are rotated in a desired manner, such as from an electricmotor and speed reduction gear train 11 from which the drive shaft 12 isjournalled in a bearing 13 and ends in a hexagonal or square tip 14 thatfits snugly in a correspondingly shaped socket centrally of the righthand face of the core 2 in FIG. 3. The left hand face of the core 2 inFIG. 3 bears a cylindrical aperture in which a stub shaft 15 seats.

The refractory discs 1 on the core 2 are borne by supports 16 and 17with the support 17 provided with suitable means such as the springloaded or lockable hinge 18 for accomplishing the assembly anddisassembly of the refractory discs 1 and the core 2 between theirsupports when the refractory material of the discs 1 has been convertedinto filaments and the discs are to be replaced.

The drive shaft 12 is connected by a chain 20 to a driven shaft 21 thatis journalled in the supports 22 and 23 that are back of the supports 16and 17. The driven shaft 21 is connected by chains 24 and 25 to a seconddriven shaft 26 on which drums 27 and 28 are mounted. Cords 29 and 30wind on the drums 27 and 28 to lower a bar 31 against the yieldingresistance of coil springs 32 and 33 housed in the upper ends of thesupports 22 and 23. The bar 31 carries the gas line 7 and doctor blades4 that are lowered to follow the decreasing diameter of the discs l asthe filaments 5 carry away the refractory material of which the discsare made. The motor 10 and gear train 11 are mounted on the supports 34,35, 36 and 37.

In lieu of the acetylene flame 3 a plasma flame may be used. A plasmaflame is obtained by passing a gas, such as argon, helium or nitrogenthrough an electric are 4 nozzle. The Encyclopedia of Chemistry(Supplement) by G. L. Clark and G. G. Hawley published in 1958 by theReinhold Publishing Corporation, New York City, New York, on page 226,elaborates on the term plasma.

It is to be understood that the method that is disclosed herein for theproduction of filaments of refractory material may be modified somewhatwithin the scope of the present invention and with apparatus other thanthat shown in the accompanying drawing.

I claim:

1. The process of drawing a filament from a disc of solid refractorymaterial having a peripheral edge, by imparting rotary motion to thedisc of solid refractory material, applying heat to the refractorymaterial peripheral edge from a source of heat as the refractorymaterial peripheral edge continuously moves past the heat source at arate that permits the part of the refractory material to which the heatsource is applied to change locally from the solid state to the liquidstate, maintaining a liquid refractory material working stationarydoctor blade with its tip in the liquid state portion of the refractorymaterial disc as the molten refractory material is carried past thestationary doctor blade, and withdrawing a filament of refractorymaterial from the worked area of molten material at the peripheral edgeof the disc while the disc is rotating.

2. The process defined by the above claim 1 applied to silica as therefractory material.

3. The process defined by the above claim 1 applied to aluminosilicateas the refractory material.

4. The process defined by the above claim 1 applied to a refractorymaterial having the composition by weight of 55% silica, 41% alumina,and 4% zirconia.

. 5. The process defined by the above claim 1 for producing filaments ofrefractory material, inclusive of the step of passing the filamentsthrough a mixture of starch in lubricating oil as a surface conditionerthereof.

6. The process of drawing a refractory fiber from a continuously movingmolten pool of refractory material in a groove on the peripheral edge ofa continuously rotating disc of the refractory material by continuouslyrotating a disc of solid refractory material having a peripheral edge,applying a flame from a fixed flame source to a limited area on thecontinuously moving peripheral edge of the disc of solid refractorymaterial that is moving at a sufiiciently slow rate to permit the flameto form a puddle of liquid refractory material in the groove on theperipheral edge of the disc of solid refractory material, continuouslyworking the puddle of liquid refractory material as it leaves contactwith the flame by the curved tip of a fixed doctor blade that extendsinto the groove on the peripheral edge of the continuously rotatingdisc, and continuously withdrawing a fiber of the refractory materialfrom the disc groove after the material has moved past the doctor blade.

References Cited in the file of this patent UNITED STATES PATENTS1,580,199 Hering Apr. 13, 1926 2,313,296 Lamesch Mar. 9, 1943 2,514,627Cook July 11, 1950 2,780,890 Russell Feb. 12, 1957

6. THE PROCESS OF DRAWING A REFRACTORY FIBER FROM A CONTINUOUSLY MOVINGMOLTEN POOL OF REFRACTORY MATERIAL IN A GROOVE ON THE PERIPHERAL EDGE OFA CONTINUOUSLY ROTATING DISC OF THE REFRACTORY MATERIAL BY CONTINUOUSLYROTATING A DISC OF SOLID REFRACTORY MATERIAL HAVING A PERIPHERAL